Hello have a problem with my gpz she started half a year ago to rukels the worst in the lower drezahl range and the left spark plug is heavily worn.On top of that I have replaced the carburettor ultrasonic cleaned ferschleisile (sealings) spark plugs exchanged halter dived,new ignition cable blus stekker and the ignition coil swapped and there was no improvement.Has vileicht an idea what I missed or what it might be.